Definition: In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
Input: ['5725', '4573', 'z', '1849', '1977', 'y', 'p', 'c', '5171']

c, p, y, z